U.S. patent application number 12/181479 was filed with the patent office on 2009-02-05 for liquid crystal display device comprising color polarizing plate.
This patent application is currently assigned to Casio Computer Co., Ltd.. Invention is credited to Norihiro Arai, Kunpei Kobayashi, Toshiharu Nishino.
Application Number | 20090033838 12/181479 |
Document ID | / |
Family ID | 40331603 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090033838 |
Kind Code |
A1 |
Kobayashi; Kunpei ; et
al. |
February 5, 2009 |
LIQUID CRYSTAL DISPLAY DEVICE COMPRISING COLOR POLARIZING PLATE
Abstract
A liquid crystal display device includes a pair of substrates,
electrodes formed on the opposing surfaces of the pair of
substrates, and a liquid crystal layer twisted in the gap between
the pair of substrates at a predetermined twisted angle. A normal
polarizing plate to exhibit a polarizing function for the whole
visible light is arranged on the outer surface of an observation
side substrate in the pair of substrates. A color polarizing plate
to exhibit a polarizing function for visible light of a wavelength
band other than a specific wavelength band is arranged on the outer
surface of the opposite side substrate in the pair of substrates. A
reflecting plate to reflect light entering from the observation
side toward the observation side is arranged on a surface of the
color polarizing plate that is opposite to the surface that opposes
the opposite side substrate.
Inventors: |
Kobayashi; Kunpei;
(Tachikawa-shi, JP) ; Nishino; Toshiharu;
(Hamura-shi, JP) ; Arai; Norihiro; (Hino-shi,
JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
220 Fifth Avenue, 16TH Floor
NEW YORK
NY
10001-7708
US
|
Assignee: |
Casio Computer Co., Ltd.
Tokyo
JP
|
Family ID: |
40331603 |
Appl. No.: |
12/181479 |
Filed: |
July 29, 2008 |
Current U.S.
Class: |
349/97 |
Current CPC
Class: |
G02F 1/133567 20210101;
G02F 2203/34 20130101; G02F 1/133533 20130101 |
Class at
Publication: |
349/97 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2007 |
JP |
2007-199558 |
Claims
1. A liquid crystal display device comprising: a pair of substrates
including an observation side substrate and an opposite side
substrate that are arranged to oppose each other at a predetermined
gap; a liquid crystal layer that is sealed in the gap between the
pair of substrates and includes liquid crystal molecules that are
twisted between the pair of substrates at a predetermined twisted
angle; electrodes that are respectively provided on inner surfaces
of the pair of substrates that oppose the liquid crystal layer and
to which a voltage to control an aligned state of the liquid
crystal molecule is applied at opposing regions; a normal
polarizing plate that is arranged on an outer surface of the
observation side substrate, and transmits a light component
oscillating within a plane parallel to a direction of a
predetermined transmission axis, and absorbs a light component
perpendicular to the transmission axis, among wavelength light of a
substantial whole band of a visible light band; a color polarizing
plate that is arranged on an outer surface of the opposite side
substrate, and transmits a light component oscillating within an
oscillation plane parallel to a predetermined transmission axis,
and absorbs a light component perpendicular to the transmission
axis, among wavelength light in a remaining band of the visible
light band excluding a specific band; and a reflecting plate that
is arranged on a surface of the color polarizing plate that is
opposite to a surface that opposes the opposite side substrate and
reflects light entering from the observation side to the
observation side.
2. The device according to claim 1, wherein the normal polarizing
plate is arranged so that a transmission axis thereof is in a
direction substantially perpendicular or parallel to an aligning
direction of the liquid crystal molecules in the vicinity of the
observation side substrate, and the color polarizing plate is
arranged so that a transmission axis thereof is aligned in the
direction substantially parallel or perpendicular to the aligning
direction of the liquid crystal molecules in the vicinity of the
observation side substrate.
3. The device according to claim 1, wherein the liquid crystal
molecules of the liquid crystal layer are twisted between the pair
of substrates at substantially a twisted angle of 90.degree., and
the normal polarizing plate and the color polarizing plate are
arranged so that transmission axes thereof are substantially
perpendicular to each other.
4. The device according to claim 1, wherein the liquid crystal
molecules of the liquid crystal layer are twisted between the pair
of substrates at substantially a twisted angle of 90.degree., and
the normal polarizing plate and the color polarizing plate are
arranged so that transmission axes thereof are substantially
parallel to each other.
5. The device according to claim 1, wherein the color polarizing
plate comprises a red color polarizing plate having a polarizing
function, for light of a wavelength band other than a wavelength
band corresponding to red in the visible light, of transmitting a
linearly polarized component parallel to the transmission axis and
absorbing a light component perpendicular to the transmission axis,
and is configured to perform display of three colors including red
in a wavelength band not polarized by the red color polarizing
plate, substantial white with which an intensity of emerging light
of a substantial whole band of the visible light wavelength band is
high, and substantial black with which the intensity of the
emerging light of substantially the whole band of the visible light
wavelength band is low.
6. The device according to claim 1, further comprising a diffusion
film that diffuses incident light and outputs diffused light and is
arranged between the opposite side substrate and the color
polarizing plate.
7. A liquid crystal display device comprising: a pair of substrates
including an observation side substrate and an opposite side
substrate that are arranged to oppose each other at a predetermined
gap; a liquid crystal layer that is sealed in the gap between the
pair of substrates and includes liquid crystal molecules that are
twisted between the pair of substrates substantially at a twisted
angle of 90.degree.; electrodes that are respectively provided on
inner surfaces of the pair of substrates that oppose the liquid
crystal layer and to which a voltage to control an aligned state of
the liquid crystal molecule is applied at opposing regions; a
normal polarizing plate that is arranged on an outer surface of the
observation side substrate so that a transmission axis thereof is
substantially parallel to an aligning direction of the liquid
crystal molecules in the vicinity of the observation side
substrate, and transmits a light component oscillating within a
plane parallel to a direction of the predetermined transmission
axis, and absorbs a light component perpendicular to the
transmission axis, among wavelength light of a substantial whole
band of a visible light band; a color polarizing plate that is
arranged on an outer surface of the opposite side substrate so that
a transmission axis thereof is substantially parallel to the
aligning direction of the liquid crystal molecules in the vicinity
of the opposite side substrate, and transmits a linearly polarized
light component parallel to the transmission axis, and absorbs a
light component perpendicular to the transmission axis, among
wavelength light in a remaining band of the visible light band
excluding a band corresponding to red; and a reflecting plate that
is arranged on a surface of the color polarizing plate that is
opposite to a surface that opposes the opposite side substrate and
reflects light entering from the observation side to the
observation side.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2007-199558,
filed Jul. 31, 2007, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a liquid crystal display
device that performs color display using a color polarizing
plate.
[0004] 2. Description of the Related Art
[0005] As a liquid crystal display device, one is known that
comprises a color polarizing plate to exhibit a polarizing function
for light of a wavelength band other than a specific band in a
visible light band and that performs color display by means of
wavelength light transmitted through the color polarizing plate
(see Jpn. Pat. Appln. KOKAI Publication No. 2003-255327).
[0006] The conventional liquid crystal display device comprising
the color polarizing plate can, however, perform simple two-color
display using one of white and black, and color display via the
color polarizing plate.
BRIEF SUMMARY OF THE INVENTION
[0007] A liquid crystal display device according to the first
aspect of the present invention includes:
[0008] a pair of substrates including an observation side substrate
and an opposite side substrate that are arranged to oppose each
other at a predetermined gap;
[0009] a liquid crystal layer that is sealed in the gap between the
pair of substrates and includes liquid crystal molecules that are
twisted between the pair of substrates at a predetermined twisted
angle;
[0010] electrodes that are respectively provided on inner surfaces
of the pair of substrates that oppose the liquid crystal layer and
to which a voltage to control an aligned state of the liquid
crystal molecule is applied at opposing regions;
[0011] a normal polarizing plate that is arranged on an outer
surface of the observation side substrate, and transmits a light
component oscillating within a plane parallel to a direction of a
predetermined transmission axis, and absorbs a light component
perpendicular to the transmission axis, among wavelength light of a
substantial whole band of a visible light band;
[0012] a color polarizing plate that is arranged on an outer
surface of the opposite side substrate, and transmits a light
component oscillating within an oscillation plane parallel to a
predetermined transmission axis, and absorbs a light component
perpendicular to the transmission axis, among wavelength light in a
remaining band of the visible light band excluding a specific band;
and
[0013] a reflecting plate that is arranged on a surface of the
color polarizing plate that is opposite to a surface that opposes
the opposite side substrate and reflects light entering from the
observation side to the observation side.
[0014] A liquid crystal display device according to the second
aspect of the present invention includes:
[0015] a pair of substrates including an observation side substrate
and an opposite side substrate that are arranged to oppose each
other at a predetermined gap;
[0016] a liquid crystal layer that is sealed in the gap between the
pair of substrates and includes liquid crystal molecules that are
twisted between the pair of substrates substantially at a twisted
angle of 90.degree.;
[0017] electrodes that are respectively provided on inner surfaces
of the pair of substrates that oppose the liquid crystal layer and
to which a voltage to control an aligned state of the liquid
crystal molecule is applied at opposing regions;
[0018] a normal polarizing plate that is arranged on an outer
surface of the observation side substrate so that a transmission
axis thereof is substantially parallel to an aligning direction of
the liquid crystal molecules in the vicinity of the observation
side substrate, and transmits a light component oscillating within
a plane parallel to a direction of the predetermined transmission
axis, and absorbs a light component perpendicular to the
transmission axis, among wavelength light of a substantial whole
band of a visible light band;
[0019] a color polarizing plate that is arranged on an outer
surface of the opposite side substrate so that a transmission axis
thereof is substantially parallel to the aligning direction of the
liquid crystal molecules in the vicinity of the opposite side
substrate, and transmits a linearly polarized light component
parallel to the transmission axis, and absorbs a light component
perpendicular to the transmission axis, among wavelength light in a
remaining band of the visible light band excluding a band
corresponding to red; and
[0020] a reflecting plate that is arranged on a surface of the
color polarizing plate that is opposite to a surface that opposes
the opposite side substrate and reflects light entering from the
observation side to the observation side.
[0021] Advantages of the invention will be set forth in the
description that follows, and in part will be obvious from the
description, or may be learned by practice of the invention.
Advantages of the invention may be realized and obtained by means
of the instrumentalities and combinations particularly pointed out
hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0022] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0023] FIG. 1 is a sectional view of a liquid crystal display
device according to an embodiment of the present invention;
[0024] FIG. 2 shows the aligning treatment directions of a pair of
substrates and the directions of the transmission axes of a normal
polarizing plate and a red polarizing plate of the liquid crystal
display device;
[0025] FIGS. 3A, 3B, and 3C are schematic views each showing a
change in polarized state of light entering from the observation
side of one pixel portion of the liquid crystal display device, in
which FIG. 3A shows a change in polarized state obtained when
applying a voltage V.sub.1, which aligns the liquid crystal
molecules to an initial twisted state to be inclined most with
respect to the substrate surfaces, across electrodes, FIG. 3B shows
a change in polarized state obtained when applying a halftone
voltage V.sub.2, which aligns the liquid crystal molecules to a
twisted state to rise obliquely with respect to the surfaces of
substrates 1 and 2, across the electrodes, and FIG. 3C shows a
change in polarized state obtained when applying a voltage V.sub.3,
which aligns the liquid crystal molecules to rise at an angle
almost perpendicular to the substrate surfaces, across the
electrodes;
[0026] FIG. 4 shows the relationship between the voltage applied to
the liquid crystal display device and the intensities of green
light, blue light, and red light emerging to the observation side;
and
[0027] FIG. 5 shows the relationship between the voltage applied to
the liquid crystal display device according to another embodiment
in which a normal polarizing plate and a red polarizing plate are
arranged so that their transmission axes are substantially parallel
to each other, and the intensities of green light, blue light, and
red light emerging to the observation side.
DETAILED DESCRIPTION OF THE INVENTION
[0028] FIG. 1 is a sectional view of a liquid crystal display
device according to an embodiment of the present invention. As
shown in FIG. 1, this liquid crystal display device comprises a
pair of substrates 1 and 2 including the observation side (upper
side in FIG. 1) transparent substrate 1 and the opposite side
transparent substrate 2, and a liquid crystal layer 3 sealed in the
gap between the pair of substrates 1 and 2. The transparent
substrates land 2 are arranged to oppose each other at a
predetermined gap. The liquid crystal layer 3 includes liquid
crystal molecules 3a (see FIGS. 3A, 3B, and 3C), which are twisted
between the pair of substrates 1 and 2 at predetermined twisted
angles. The pair of substrates 1 and 2 are respectively provided
with transparent electrodes 4 and 5 on their inner surfaces
opposing the liquid crystal layer 3. The opposing regions of the
transparent electrodes 4 and 5 form pixel portions, in which the
aligned state of the liquid crystal molecules 3a is controlled by
an applied voltage. A normal polarizing plate 9 is arranged on the
outer surface of the observation side substrate 1. The normal
polarizing plate 9 is to transmit a light component oscillating
within a plane parallel to the direction of a predetermined
transmission axis, and to absorb a light component perpendicular to
the transmission axis, among wavelength light of a substantial
whole band of the visible light band. The outer surface of the
opposite side substrate 2 is provided with a color polarizing plate
10 and a reflecting plate 11. The color polarizing plate 10 is to
transmit a light component oscillating within an oscillation plane
parallel to a predetermined transmission axis, and to absorb a
light component perpendicular to the transmission axis, among the
wavelength light in a remaining band of the visible light band
excluding a specific band. The reflecting plate 11 is arranged on
that surface of the color polarizing plate 10 that is opposite to
the surface that the opposes the substrate 2, and is to reflect
light entering from the observation side to the observation
side.
[0029] The liquid crystal display device of this embodiment is an
active matrix liquid crystal display device, which includes pixel
electrodes 5 that is formed on the inner surface of the substrate 2
that is opposite to the observation side in a matrix fashion with
being aligned in row and column directions, and a film-like opposed
electrode 4 that is formed on the inner surface of the observation
side substrate 1 corresponding to the aligned regions of the pixel
electrodes 5. Although not shown in FIG. 1, TFTs (Thin Film
Transistors) respectively connected to the pixel electrodes 5 are
arranged on the inner surface of the opposite side substrate 2
corresponding to the pixel electrodes 5. Scanning lines to supply
gate signals to the TFTs of the respective rows and signal lines to
supply data signals to the TFTs of the respective columns are
provided to the inner surface of the opposite side substrate 2
through the TFTs.
[0030] The pair of substrates 1 and 2 are respectively provided
with aligning films 6 and 7 on their inner surfaces covering the
electrodes 4 and 5, and the film surfaces of the aligning films 6
and 7 are rubbed in predetermined directions, subjected to the
aligning treatment.
[0031] The pair of substrates 1 and 2 are bonded to each other
through a frame-like seal member 8 formed to surround the aligned
region of the pixel electrodes 5. The liquid crystal layer 3
comprising a nematic liquid crystal having a negative dielectric
anisotropy is sealed in the region between the substrates 1 and 2
that is surrounded by the seal member 8.
[0032] The liquid crystal molecules 3a of the liquid crystal layer
3 are aligned in the vicinities of the pair of substrates 1 and 2
so that their molecular major axes are aligned with the aligning
treatment directions (the rubbing directions of the aligning films
6 and 7) of the substrates 1 and 2, and are twisted between the
pair of substrates 1 and 2 with a twisted angle corresponding to
the angle of intersection of the aligning treatment directions (the
rubbing directions of the aligning films 6 and 7) 1a and 2a (see
FIG. 2) of the respective substrates 1 and 2.
[0033] The normal polarizing plate 9 has a transmission axis 9a
(see FIG. 2) in a predetermined direction within a plane parallel
to its plate surface. The normal polarizing plate 9 exhibits a
polarizing function, for the wavelength light of the whole band of
the visible light band, of transmitting light having an oscillation
component in a direction parallel to the transmission axis 9a, and
absorbing light having an oscillation component in a direction
perpendicular to the transmission axis 9a.
[0034] The color polarizing plate 10 has a transmission axis 10a
(see FIG. 2) in a predetermined direction within a plane parallel
to its plate surface. The color polarizing plate 10 has a
polarizing function, for the wavelength light of the remaining band
of the visible light band excluding the specific band, of
transmitting light having an oscillation component in a direction
parallel to the transmission axis 10a, and absorbing light having
an oscillation component in a direction perpendicular to the
transmission axis 10a, and transmits the wavelength light of the
specific band without polarization. The color polarizing plate 10
is, e.g., a polarizing plate to exhibit a polarizing function for
the light of a wavelength band other than the red wavelength band
in the visible light band, of transmitting a linearly polarized
component that is parallel to the transmission axis 10a, and
absorbing a light component perpendicular to the transmission axis
10a. This color polarizing plate 10 will be called a red polarizing
plate hereinafter.
[0035] The normal polarizing plate 9 is arranged so that its
transmission axis 9a is in a direction substantially parallel or
perpendicular to the aligning direction of the liquid crystal
molecules 3a in the vicinity of the observation side substrate 1.
The red polarizing plate 10 is arranged so that its transmission
axis 10a is in a direction substantially parallel or perpendicular
to the aligning direction of the liquid crystal molecules 3a in the
vicinity of the opposite side substrate 1.
[0036] FIG. 2 shows aligning treatment directions 1a and 2a of the
pair of substrates 1 and 2 and the directions of the transmission
axes 9a and 10a of the normal polarizing plate 9 and the red
polarizing plate 10. In this embodiment, the substrates 1 and 2 are
arranged so that their aligning treatment directions 1a and 2a
intersect substantially at the angle of 90.degree.. The liquid
crystal molecules 3a of the liquid crystal layer 3 are twisted
between the pair of substrates 1 and 2 so that the twisted
directions of the molecular orientations between the substrates 1
and 2 are twisted to form a twisted angle of substantially
90.degree., as indicated by a broken arrow in FIG. 2.
[0037] The value of a product .DELTA.nd of a liquid crystal
anisotropic refractive index .DELTA.n and a liquid crystal layer
thickness d of the liquid crystal layer 3 is set at such an angle
that, in the initial alignment state in which the liquid crystal
molecules 3a are twisted between the pair of substrates 1 and 2 at
the twisted angle of substantially 90.degree., linearly polarized
light having a wavelength of 550 nm is rotated through
substantially 90.degree. with reference to 550 nm as the halftone
wavelength of the halftone wavelength band of the visible light
band.
[0038] In this embodiment, the normal polarizing plate 9 and red
polarizing plate 10 are arranged so that the respective
transmission axes 9a and 10a are substantially perpendicular to
each other, that the transmission axis 9a of the normal polarizing
plate 9 is substantially parallel to the aligning treatment
direction 1a of the observation side substrate 1, that is, the
aligning direction of the liquid crystal molecules 3a in the
vicinity of the observation side substrate 1, and that the
transmission axis 10a of the red polarizing plate 10 is
substantially parallel to the aligning treatment direction 2a of
the opposite side substrate 2, that is, the aligned direction of
the liquid crystal molecules 3a in the vicinity of the opposite
side substrate 2.
[0039] Furthermore, this liquid crystal display device comprises a
diffusion layer 12 that is arranged between the opposite side
substrate 2 and red polarizing plate 10 to diffuse transmitted
light.
[0040] This liquid crystal display device performs reflection
display utilizing external light that is the light in the
atmosphere where the liquid crystal display device is used. Light
entering from the observation side, transmitted through the normal
polarizing plate 9, liquid crystal layer 3, and red polarizing
plate 10, reflected by the reflecting plate 11, and further
transmitted through the red polarizing plate 10, liquid crystal
layer 3, and normal polarizing plate 9 emerges to the observation
side.
[0041] FIGS. 3A, 3B, and 3C are schematic views each showing a
change in polarized state of light entering from the observation
side of one pixel portion of the liquid crystal display device.
FIG. 3A shows a change in polarized state obtained when applying a
voltage (a voltage of substantially 0 V) V.sub.1, which aligns the
liquid crystal molecules 3a to an initial twisted state to be
inclined most with respect to the surfaces of the substrates 1 and
2, across the electrodes 4 and 5. FIG. 3B shows a change in
polarized state obtained when applying a halftone voltage V.sub.2,
which aligns the liquid crystal molecules 3a to a twisted state to
rise obliquely with respect to the surfaces of the substrates 1 and
2, across the electrodes 4 and 5. FIG. 3C shows a change in
polarized state obtained when applying a voltage V.sub.3, which
aligns the liquid crystal molecules 3a to rise at an angle almost
perpendicular to the surfaces of the substrates 1 and 2, across the
electrodes.
[0042] FIGS. 3A, 3B, and 3C also schematically show a shift in
polarized state of light in the red band and light in the blue band
with respect to the polarized state of light in the green band.
This shift occurs due to the wavelength dependency of the double
refraction birefringence function of the liquid crystal layer 3
when the value of .DELTA.nd of the liquid crystal layer 3 is set
with reference to the wavelength of 550 nm (green) that is the
center wavelength of the visible light band.
[0043] As shown in FIGS. 3A, 3B, and 3C, non-polarized white light
W.sub.0 entering the liquid crystal display device from the
observation side is polarized by the normal polarizing plate 9, and
enters the liquid crystal layer 3 as linearly polarized light
W.sub.1 parallel to the transmission axis 9a of the normal
polarizing plate 9.
[0044] First, the polarized state of each portion will be described
that is obtained when applying the voltage V.sub.1, which aligns
the liquid crystal molecules 3a almost to the initial twisted state
to be inclined most with respect to the surfaces of the substrates
1 and 2, across the transparent electrodes 4 and 5. As shown in
FIG. 3A, the white linearly polarized light W.sub.1 entering the
liquid crystal layer 3 is rotated through substantially 90.degree.
by the double refraction birefringence function of the liquid
crystal layer 3.
[0045] More specifically, of the white linearly polarized light
W.sub.1 entering the liquid crystal layer 3, the wavelength light
in the intermediate wavelength band, that is, green light, is
rotated through substantially 90.degree., and emerges from the
liquid crystal layer 3 as linearly polarized light G.sub.1 having a
polarization plane in a direction parallel to the transmission axis
10a of the red polarizing plate 10. Wavelength light in a
wavelength band shorter than the intermediate wavelength band, that
is, blue light, and wavelength light in a wavelength band longer
than the intermediate wavelength band, that is, red light, emerge
from the liquid crystal layer 3 respectively as elliptically
polarized light B.sub.1 and elliptically polarized light R.sub.1
having major axes in directions shifted in opposite directions (the
clockwise direction and counterclockwise direction as viewed from
the observation side) with respect to the polarization plane of the
green linearly polarized light G.sub.1 at an angle corresponding to
the wavelength dependency of the double refraction birefringence
function of the liquid crystal layer 3.
[0046] In this case, the shifts of the major axes and the lengths
of the minor axes of the blue elliptically polarized light B.sub.1
and red elliptically polarized light R.sub.1 are very small. Hence,
each of the blue elliptically polarized light B.sub.1 and red
elliptically polarized light R.sub.1 can be regarded as linearly
polarized light having a polarization plane substantially parallel
to that of the green linearly polarized light G.sub.1.
[0047] The green light G.sub.1, blue light B.sub.1, and red light
R.sub.1 rotated by the liquid crystal layer 3 enter the red
polarizing plate 10. The green linearly polarized light G.sub.1
having the polarization plane parallel to the transmission axis 10a
of the red polarizing plate 10, light B.sub.2, of the blue
elliptically polarized light B.sub.1, having an oscillation
component parallel to the transmission axis 10a of the red
polarizing plate 10, and the red elliptically polarized light
R.sub.1 that is not polarized by the red polarizing plate 10 are
transmitted through the red polarizing plate 10 and reflected by
the red polarizing plate 10.
[0048] Subsequently, the light G.sub.1, light B.sub.2, and light
R.sub.1 of the respective colors reflected by the reflecting plate
11 are transmitted through the red polarizing plate 10 to enter the
liquid crystal layer 3 again, and are subjected to the double
refraction birefringence function of the liquid crystal layer 3.
More specifically, the green linearly polarized light G.sub.1 forms
linearly polarized light G.sub.2 having a polarization plane
rotated through substantially 90.degree.. The blue light B.sub.2
parallel to the transmission axis 10a of the red polarizing plate
10, and the red elliptically polarized light R.sub.1 respectively
form elliptically polarized light B.sub.3 and elliptically
polarized light R.sub.2 slightly shifted in opposite directions
with respect to the polarization plane of the rotated green
linearly polarized light G.sub.2 at an angle corresponding to the
wavelength dependency of the double refraction birefringence
function of the liquid crystal layer 3. Then, the polarized light
G.sub.2, polarized light B.sub.3, and polarized light R.sub.2
emerge from the liquid crystal layer 3.
[0049] The light G.sub.2, light B.sub.3, and light R.sub.2 of the
respective colors emerging from the liquid crystal layer 3 enter
the normal polarizing plate 9. The green linearly polarized light
G.sub.2, light B.sub.4, of the blue elliptically polarized light
B.sub.3, having an oscillation component parallel to the
transmission axis 9a of the normal polarizing plate 9, and light
R.sub.3, of the red elliptically polarized light R.sub.2, having an
oscillation component parallel to the transmission axis 9a of the
normal polarizing plate 9 are transmitted through the normal
polarizing plate 9 and emerge to the observation side.
[0050] When compared to the blue elliptically polarized light
B.sub.1 and red elliptically polarized light R.sub.1 that enter
from the observation side and emerge from the liquid crystal layer
3 toward the red polarizing plate 10, the blue elliptically
polarized light B.sub.3 and red elliptically polarized light
R.sub.2 have longer minor axes. The light intensity of each
oscillation component of the elliptically polarized light B.sub.3
and elliptically polarized light R.sub.2 that are parallel to the
polarization plane of the green linearly polarized light G.sub.2 is
not largely different from the intensity of the green linearly
polarized light G.sub.2, and can accordingly be regarded
substantially the same as that.
[0051] Hence, when applying the voltage V.sub.1, which aligns the
liquid crystal molecules 3a to the initial twisted state to be
inclined most with respect to the surfaces of the substrates 1 and
2, across the transparent electrodes 4 and 5, light in which the
green light G.sub.2, blue light B.sub.4, and red light R.sub.3 have
substantially the same intensity, emerges from the normal
polarizing plate 9. The light G.sub.2, light B.sub.4, and light
R.sub.3 mix to display white.
[0052] The polarized state of each portion will be described that
is obtained when applying the halftone voltage V.sub.2, which
aligns the liquid crystal molecules 3a to the twisted state to rise
obliquely with respect to the surfaces of the substrates 1 and 2,
across the transparent electrodes 4 and 5. As shown in FIG. 3B, of
the white linearly polarized light W.sub.1 transmitted through the
normal polarizing plate 9 from the observation side and entering
the liquid crystal layer 3, the green light, blue light, and red
light are subjected to the double refraction birefringence function
corresponding to the rise angle of the liquid crystal molecules. 3a
of the liquid crystal layer 3, and emerge from the liquid crystal
layer 3 as elliptically polarized light G.sub.11, elliptically
polarized light B.sub.11, and elliptically polarized light
R.sub.11, respectively.
[0053] When compared to the green linearly polarized light G.sub.1,
blue elliptically polarized light B.sub.1, and red elliptically
polarized light R.sub.1 emerging from the liquid crystal layer 3
when applying the voltage V.sub.1 across the transparent electrodes
4 and 5 as shown in FIG. 3A, the green elliptically polarized light
G.sub.11, blue elliptically polarized light B.sub.11, and red
elliptically polarized light R.sub.11 are elliptically polarized
light having major axes with different tilts and longer minor
axes.
[0054] The green elliptically polarized light G.sub.11, blue
elliptically polarized light B.sub.11, and red elliptically
polarized light R.sub.11 that have been subjected to the double
refraction birefringence function of the liquid crystal layer 3
enter the red polarizing plate 10. Light G.sub.12, of the green
elliptically polarized light G.sub.11, having an oscillation
component parallel to the transmission axis 10a of the red
polarizing plate 10, light B.sub.12, of the blue elliptically
polarized light B.sub.11, having an oscillation component parallel
to the transmission axis 10a of the red polarizing plate 10, and
the red elliptically polarized light R.sub.11 that is not polarized
by the red polarizing plate 10 emerge from the red polarizing plate
10 and are reflected by the reflecting plate 11.
[0055] Hence, each of the light B.sub.12 and light G.sub.12
emerging from the red polarizing plate 10 is light having a light
intensity lower than that of each of the green linearly polarized
light G.sub.1, blue elliptically polarized light B.sub.2, and red
elliptically polarized light R.sub.1 shown in FIG. 3A.
[0056] The light G.sub.12, light B.sub.12, and light R.sub.11 of
the respective colors reflected by the reflecting plate 11 are
transmitted through the red polarizing plate 10 and enter the
liquid crystal layer 3 again, and emerge from the liquid crystal
layer 3 as elliptically polarized light G.sub.13, elliptically
polarized light B.sub.13, and elliptically polarized light R.sub.12
according to the double refraction birefringence function
corresponding to the rise angle of the liquid crystal molecules 3a
of the liquid crystal layer 3, respectively.
[0057] The elliptically polarized light G.sub.13, elliptically
polarized light B.sub.13, and elliptically polarized light R.sub.12
of the respective colors emerging from the liquid crystal layer 3
and entering the normal polarizing plate 9 emerge from the normal
polarizing plate 9 toward the observation side as light G.sub.14,
of the green elliptically polarized light G.sub.13, having an
oscillation component parallel to the transmission axis 9a of the
normal polarizing plate 9, light B.sub.14, of the blue elliptically
polarized light B.sub.13, having an oscillation component parallel
to the transmission axis 9a of the normal polarizing plate 9, and
light R.sub.13, of the red elliptically polarized light R.sub.12,
having an oscillation component parallel to the transmission axis
9a of the normal polarizing plate 9, respectively.
[0058] Each of the green light, blue light, and red light emerging
to the observation side, that is, the linearly polarized light
G.sub.14, linearly polarized light B.sub.14, and linearly polarized
light R.sub.13 parallel to the transmission axis 9a of the normal
polarizing plate 9 is light having a very low intensity. When
applying the halftone voltage V.sub.2, which aligns the liquid
crystal molecules 3a to the twisted state to rise obliquely with
respect to the surfaces of the substrates 1 and 2, across the
transparent electrodes 4 and 5, the light exit rate becomes lowest,
and substantially black is displayed.
[0059] The polarized state of each portion will now be described
that is obtained when applying the voltage V.sub.3, which aligns
the liquid crystal molecules 3a to be substantially perpendicular
to the surfaces of the substrates 1 and 2, across the transparent
electrodes 4 and 5. As shown in FIG. 3C, the white linearly
polarized light W.sub.1 entering from the observation side and
transmitted through the normal polarizing plate 9 is transmitted
through the liquid crystal layer 3 without being subjected to the
double refraction birefringence function, and enters the red
polarizing plate 10. The red polarizing plate 10 absorbs green
light and blue light of the white linearly polarized light W.sub.1,
and red light is transmitted through the red polarizing plate
10.
[0060] Red linearly polarized light R.sub.21 transmitted through
the red polarizing plate 10 is reflected by the reflecting plate
11, and transmitted through the red polarizing plate 10, liquid
crystal layer 3, and normal polarizing plate 9 sequentially to
emerge to the observation side.
[0061] Therefore, when applying the voltage V.sub.3, which aligns
the liquid crystal molecules 3a to be substantially perpendicular
to the surfaces of the substrates 1 and 2, across the transparent
electrodes 4 and 5, only the red linearly polarized light R.sub.21
emerges to the observation side to display red.
[0062] FIG. 4 shows the relationship between the voltage applied to
the liquid crystal display device of this embodiment and the
intensities of green light, blue light, and red light emerging to
the observation side. As shown in FIG. 4, the liquid crystal
display device of this embodiment becomes the brightest to display
white when applying the voltage V.sub.1, which aligns the liquid
crystal molecules 3a to the initial twisted state to be inclined
most with respect to the surfaces of the substrates 1 and 2, across
the electrodes 4 and 5. The intensities of the green light, blue
light, and red light become the lowest, when applying the halftone
voltage V.sub.2, which aligns the liquid crystal molecules 3a to
the twisted state to rise obliquely with respect to the surfaces of
the substrates 1 and 2, across the transparent electrodes 4 and 5,
and the liquid crystal display device displays black. The liquid
crystal display device displays red when applying the voltage
V.sub.3, which aligns the liquid crystal molecules 3a to be
substantially perpendicular to the surfaces of the substrates 1 and
2, across the transparent electrodes 4 and 5.
[0063] In this manner, the liquid crystal display device comprises
the liquid crystal layer 3, electrodes 4 and 5, normal polarizing
plate 9, red polarizing plate 10, and reflecting plate 11. The
liquid crystal layer 3 is sealed in the gap between the pair of
substrates 1 and 2 and includes the liquid crystal molecules 3a
that are twisted between the pair of substrates 1 and 2 at the
predetermined twisted angle. The electrodes 4 and 5 are provided on
the inner surfaces of the pair of substrates 1 and 2 that oppose
the liquid crystal layer 3 and to which the voltage to control the
aligned state of the liquid crystal molecules 3a at the opposing
regions. The normal polarizing plate 9 is arranged on the outer
surface of the observation side substrate 1 and exhibits a
polarizing function for wavelength light of the substantial whole
band of the visible light band. The red polarizing plate 10 is
arranged on the outer surface of the opposite side substrate 2, and
exhibits a polarizing function for wavelength light of the band
other than the red wavelength band in the visible light band. The
reflecting plate 11 is arranged on the surface of the red
polarizing plate 10 that is opposite to the surface opposing the
substrate 2, and reflects light entering from the observation side
to the observation side. Hence, the liquid crystal display device
can perform tricolor display using both white and black, and red
via the red polarizing plate 10.
[0064] In the liquid crystal display device, the normal polarizing
plate 9 is arranged so that its transmission axis 9a is in the
direction substantially parallel to the aligning direction (the
aligning treatment direction 1a of the observation side substrate
1) of the liquid crystal molecules 3a in the vicinity of the
observation side substrate 1. Also, the red polarizing plate 10 is
arranged so that its transmission axis 10a is in the direction
substantially parallel to the aligning direction (the aligning
treatment direction 2a of the substrate 2) of the liquid crystal
molecules 3a in the vicinity of the opposite side substrate 2.
Accordingly, the brightness of white display and that of red
display can be increased.
[0065] Furthermore, in the liquid crystal display device, the
liquid crystal molecules 3a of the liquid crystal layer 3 are
twisted between the pair of substrates 1 and 2 at the twisted angle
of substantially 90.degree.. The normal polarizing plate 9 and red
polarizing plate 10 are arranged so that their transmission axes 9a
and 10a are substantially perpendicular to each other. Accordingly,
the contrast of white display and that of black display can be
increased.
[0066] The normal polarizing plate 9 and red polarizing plate 10
may be arranged so that the transmission axis 9a of the normal
polarizing plate 9 is substantially perpendicular to the aligning
direction of the liquid crystal molecules 3a in the vicinity of the
observation side substrate 1, and that the transmission axis 10a of
the red polarizing plate 10 is substantially perpendicular to the
aligning direction of the liquid crystal molecules 3a in the
vicinity of the opposite side substrate 2. In this case as well,
white can be displayed by applying the voltage V.sub.1, which
aligns the liquid crystal molecules 3a to the initial twisted state
to be inclined most with respect to the surfaces of the substrates
1 and 2, across the electrodes 4 and 5, black can be displayed by
applying the halftone voltage V.sub.2, which aligns the liquid
crystal molecules 3a to the twisted state to rise obliquely with
respect to the surfaces of the substrates 1 and 2, across the
electrodes 4 and 5, and red can be displayed by applying the
voltage V.sub.3, which aligns the liquid crystal molecules 3a to be
substantially perpendicular to the surfaces of the substrates 1 and
2, across the electrodes 4 and 5.
[0067] In the above embodiment, the normal polarizing plate 9 and
red polarizing plate 10 are arranged so that their transmission
axes 9a and 10a are substantially perpendicular to each other.
Alternatively, the normal polarizing plate 9 and red polarizing
plate 10 may be arranged so that their transmission axes 9a and 10a
are substantially parallel to each other.
[0068] FIG. 5 shows the relationship between the voltage applied to
a liquid crystal display device according to another embodiment in
which a normal polarizing plate 9 and a red polarizing plate 10 are
arranged so that their transmission axes 9a and 10a are
substantially perpendicular to each other, and the intensities of
green light, blue light, and red light emerging to the observation
side. As shown in FIG. 5, the liquid crystal display device
according to this embodiment displays red, black and white. Red is
displayed when applying a voltage V.sub.11, which aligns liquid
crystal molecules 3a to the initial twisted state to be inclined
most with respect to the surfaces of the substrates 1 and 2, across
electrodes 4 and 5. Black is displayed when applying a halftone
voltage V.sub.12, which aligns the liquid crystal molecules 3a to
the twisted state to rise obliquely with respect to the surfaces of
the substrates 1 and 2, across the electrodes 4 and 5. White is
displayed when applying a voltage V.sub.13, which aligns the liquid
crystal molecules 3a to be substantially perpendicular to the
surfaces of the substrates 1 and 2, across electrodes 4 and 5.
[0069] The liquid crystal display device according to the above
embodiment comprises the red polarizing plate as the color
polarizing plate. The color polarizing plate is not limited to a
red polarizing plate but may be a polarizing plate of another color
such as green or blue. If the liquid crystal display device
comprises, e.g., a green polarizing plate, it can perform tricolor
display using both white and black, and green via the color
polarizing plate.
[0070] As described above, a liquid crystal display device
according to the present invention is characterized by comprising a
pair of substrates including an observation side substrate and an
opposite side substrate that are arranged to oppose each other at a
predetermined gap, a liquid crystal layer that is sealed in the gap
between the pair of substrates and includes liquid crystal
molecules that are twisted between the pair of substrates at a
predetermined twisted angle, electrodes that are respectively
provided on inner surfaces of the pair of substrates that oppose
the liquid crystal layer and to which a voltage to control an
aligned state of the liquid crystal molecule is applied at opposing
regions, a normal polarizing plate that is arranged on an outer
surface of the observation side substrate, and transmits a light
component oscillating within a plane parallel to a direction of a
predetermined transmission axis, and absorbs a light component
perpendicular to the transmission axis, among wavelength light of a
substantial whole band of a visible light band, a color polarizing
plate that is arranged on an outer surface of the opposite side
substrate, and transmits a light component oscillating within an
oscillation plane parallel to a predetermined transmission axis,
and absorbs a light component perpendicular to the transmission
axis, among wavelength light in a remaining band of the visible
light band excluding a specific band, and a reflecting plate that
is arranged on a surface of the color polarizing plate that is
opposite to a surface that opposes the opposite side substrate and
reflects light entering from the observation side to the
observation side.
[0071] In the liquid crystal display device, preferably, the normal
polarizing plate is arranged so that a transmission axis thereof is
in a direction substantially perpendicular or parallel to an
aligning direction of the liquid crystal molecules in the vicinity
of the observation side substrate, and the color polarizing plate
is arranged so that a transmission axis thereof is aligned in the
direction substantially parallel or perpendicular to the aligning
direction of the liquid crystal molecules in the vicinity of the
observation side substrate.
[0072] Preferably, the liquid crystal molecules of the liquid
crystal layer are twisted between the pair of substrates at a
twisted angle of substantially 90.degree., and the normal
polarizing plate and the color polarizing plate are arranged so
that transmission axes thereof are substantially perpendicular to
each other.
[0073] In addition, preferably, the liquid crystal molecules of the
liquid crystal layer are twisted between the pair of substrates at
a twisted angle of substantially 90.degree., and the normal
polarizing plate and the color polarizing plate are arranged so
that transmission axes thereof are substantially parallel to each
other.
[0074] Preferably, the color polarizing plate comprises a red color
polarizing plate having a polarizing function, for light of a
wavelength band other than a wavelength band corresponding to red
in the visible light, of transmitting a linearly polarized
component parallel to the transmission axis and absorbing a light
component perpendicular to the transmission axis, and is configured
to perform display of three colors including red in a wavelength
band not polarized by the red color polarizing plate, substantial
white with which an light exit rate of a substantial whole band of
the visible light wavelength band is high, and substantial black
with which the light exit rate of the substantial whole band of the
visible light wavelength band is low.
[0075] In addition, the liquid crystal display device according to
the present invention, preferably, further comprises a diffusion
film that diffuses incident light and outputs diffused light and is
arranged between the opposite side substrate and the color
polarizing plate.
[0076] A liquid crystal display device according to the present
invention is characterized by comprising a pair of substrates
including an observation side substrate and an opposite side
substrate that are arranged to oppose each other at a predetermined
gap, a liquid crystal layer that is sealed in the gap between the
pair of substrates and includes liquid crystal molecules that are
twisted between the pair of substrates at a twisted angle of
substantially 90.degree., electrodes that are respectively provided
on inner surfaces of the pair of substrates that oppose the liquid
crystal layer and to which a voltage to control an aligned state of
the liquid crystal molecule is applied at opposing regions, a
normal polarizing plate that is arranged on an outer surface of the
observation side substrate so that a transmission axis thereof is
substantially parallel to an aligning direction of the liquid
crystal molecules in the vicinity of the observation side
substrate, and transmits a light component oscillating within a
plane parallel to a direction of the predetermined transmission
axis, and absorbs a light component perpendicular to the
transmission axis, among wavelength light of a substantial whole
band of a visible light band, a color polarizing plate that is
arranged on an outer surface of the opposite side substrate so that
a transmission axis thereof is substantially parallel to the
aligning direction of the liquid crystal molecules in the vicinity
of the opposite side substrate, and transmits a linearly polarized
light component parallel to the transmission axis, and absorbs a
light component perpendicular to the transmission axis, among
wavelength light in a remaining band of the visible light band
excluding a band corresponding to red, and a reflecting plate that
is arranged on a surface of the color polarizing plate that is
opposite to a surface that opposes the opposite side substrate and
reflects light entering from the observation side to the
observation side.
[0077] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *